1. Field of the Invention
The instant invention relates to apparatus for insulating windows and similar openings in buildings. More particularly, the instant invention relates to thermal shutters for insulating windows and similar openings through building walls.
2. Prior Art and Other Considerations
Residential and commercial space heating account for approximately twenty percent of the total national energy consumption in the United States. An estimated one-quarter to one-third of this consumption is attributable to heat losses through windows. Accordingly, about five percent of the total national energy consumption literally flows out of windows and is wasted. According to some estimates, this amounts to approximately four quadrillion btu's per year which is equivalent to approximately 700 million barrels of oil. The total fuel cost to consumers due to window heat loss is in excess of twelve billion dollars per year. To the individual homeowner or commercial building owner, reductions in heat loss through windows are immediately apparent in monthly bills.
As is readily apparent from disclosures such as that of U.S. Pat. No. 4,221,091, issued Sept. 9, 1980, there is a paucity of solutions to the problem of insulating window areas. These solutions all contain major shortcomings that the current invention cures. The subject of U.S. Pat. No. 4,221,091 is essentially a fixed exterior framing system for window insulation. It is composed of a great variety of pieces that combine in a complex manner to form a stationary object, resulting in high prices for installation. The subject of U.S. Pat. No. 4,212,289 is not really a window insulating system at all, but a solar collector disguised as a window shutter. The subject of U.S. Pat. No. 4,068,428 is simply an interior storm window. The subject of U.S. Pat. No. 4,194,550 is typical of roll-up fabric window insulation. It must be factory cut and then delivered to the site. Furthermore, as with all roll-up systems, it is impossible to achieve an effective infiltration seal along the perimeter. The subject of U.S. Pat. No. 4,115,953 is an assembly of a great many standard lumberyard components. It depends on expensive sliding door hardware, and calls upon the installer to apply weatherstripping to the completed assembly. It is a difficult construction subject to warping and a resultant failure of the seals.
Since there are an enormous number of existing structures having window areas which need insulation, the problem must be approached and solved on a retrofit basis. This requires that the installations should be compatible with existing structures and should be both inexpensive and relatively easy to install. Preferably, existing technology with plant capacity already in existence should be relied upon in order to expedite utilization of the solution.
In order to be widely adopted, there are certain constraints that a solution to this problem must contend with. For example, the apparatus should be operable from inside a building and should not be aesthetically displeasing, or at least should be as unobtrusive as possible. Moreover, the system should be easy to remove when not needed as well as being easy to install.
In designing such an apparatus, one needs to keep in mind that it is advantageous to admit sunlight in order to warm a building during the day in cool, temperate climates and to insulate windows during the evening in order to prevent the loss of heat accumulated in the building by sunlight and other means. On the other hand, during hot weather, it is frequently desirable to block sunlight from entering the building during the day and to uncover windows during the night so that a building will remain cool. It should be kept in mind that buildings in climates which have warm summers and cool winters need to operate in both modes.
In order to enhance ease of installation, the apparatus should be relatively light in weight. In order to have a long and useful life, the apparatus should be strong and durable. Moreover, the apparatus should be safe and should not present a fire hazard. If the apparatus is locked in place, one should be able to quickly remove it and open a window for both light and egress. In essence, the apparatus should not interfere to any great extent with the normal operation and function of windows while at the same time minimizing the thermal drain of windows.